This invention relates to antimicrobial proteins, processes for their manufacture and use, and DNA sequences encoding them. In particular it relates to antimicrobial proteins capable of being isolated from seeds of Aralia or Impatiens.
In this context, antimicrobial proteins are defined as proteins or peptides possessing at least one of the following activities: antifungal activity (which may include anti-yeast activity); antibacterial activity. Activity includes a range of antagonistic effects such as partial inhibition or death. Antimicrobial proteins may be oligomeric or may be single peptide units.
The genus Aralia is part of the Araliaceae, a medium-sized plant family whose best known members are ivy and ginseng. Medicinal extracts have been obtained from some Aralia species, such as Aralia cordata.
The genus Impatiens is part of the Balsaminaceae plant family. There are five hundred to six hundred Impatiens species, many of which are commercially cultivated as greenhouse or pot plants.
Plants produce a wide array of antifungal compounds to combat potential invaders and over the last ten years it has become clear that proteins with antifungal activity form an important part of these defences. Several classes of such proteins have been described including thionins, beta-1,3-glucanases, ribosome-inactivating proteins, zeamatins, chitin-binding lectins and chitinases. These proteins have gained considerable attention as they could potentially be used as biocontrol agents.
Antimicrobial proteins with activity against plant pathogenic fungi have been isolated from certain plant species. We have previously described the structural and antifungal properties of several such proteins, including:
Mj-AMP1 and Mj-AMP2 from Mirabilis jalapa seeds (Cammue BPA et al, 1992, J Biol Chem, 267:2228-2233; International Application Publication Number WO92/15691);
Ac-AMP1 and Ac-AMP2 from Amaranthus caudatus seeds (Broekaert WF et al, 1992, Biochemistry, 37:4308-4314; International Application Publication Number WO92/21699);
Ca-AMP1 from Capsicum annuum, Bm-AMP1 from Briza maxima, Da-AFP from Delphinium, Cr-AFP from Catapodium, Ba-AFP from Baptisia and Ml-AFP from Microsensis (International Patent Application Publication Number WO94/11511);
Rs-AFP1 and Rs-AFP2 from Raphanus sativus seeds (Terras FRG et al, 1992, J Biol Chem, 267:15301-13309) and related proteins such as Bn-AFP1 and Bn-AFP2 from Brassica napus, Br-AFP1 and Br-AFP2 from Brassica rapa, Sa-AFP1 and Sa-AFP2 from Sinapis alba, At-AFP1 from Arabidopsis thaliana, Dm-AMP1 and Dm-AMP2 from Dahlia merckii, Cb-AMP1 and Cb-AMP2 from Cnicus benedictus, Lc-AMP from Lathyrus cicera, Ct-AMP1 and Ct-AMP2 from Clitoria ternatea, Rs-nsLTP from Raphanus sativus (International Patent Application Publication Number WO93/05153).
These and other plant-derived antimicrobial proteins are useful as fungicides or antibiotics, particularly for agricultural purposes. The proteins may be applied to or around a plant or may be expressed within a plant.